The Underdark
by Karategal
Summary: Sequel to "An Unexpected Addition". Over ten years after Thorin was crowned King Under the Mountain, internal dissent and clan rivalry is still a major problem for the Line of Durin. After a surprise attack on their home, Bilbo and Thorin must do everything in their power to protect their mountain, their people, and their loved ones. And their nephews are the main targets.


Disclaimer: I don't own any of the characters or actors from _The Hobbit_. Everything belongs to the great and powerful J.R.R. Tolkien.

Hello, everyone! Okay, this is actually a story that I've had written for quite a while now. It's a direct sequel to _An Unexpected Addition_ that I had originally planned to merge into the main story, but then I realized that it would work much better as a stand-alone story all by itself. I would highly recommend reading _An Unexpected Addition_ first in order to understand the overall storyline; _Tales of a Disgruntled Hobbit_ would also be helpful, but not necessary unless you want extra background on several OCs and some of the Company. I've already written most of the story, but edited posts will likely be kinda slow due to my upcoming surgeries and recovery. Please try to bear with me. And several chapters of this story will be from Frodo's point of view, so I hope readers will enjoy a new perspective here.

Chapter I

* * *

"Uncle Thorin..."

The King Under the Mountain stood directly next to his youngest nephew, who was staring over the railings at Erebor's newest mithril mine. His uncle had given a very long speech just a few moments ago, and as Frodo had learned during his ten years in Erebor, dwarves _really_ liked to give long-winded speeches. Thorin himself tended to be a giant offender of this abysmal habit.

"My feet hurt."

A gentle hand tugged Frodo to the right, his small body easily fitting into the crook of Bilbo's torso. The older hobbit snuck a small biscuit into nephew's hand with a knowing wink. He'd already smuggled several to Fíli and Kíli throughout the evening. And Nori, Bofur, and Dori had found a few in their pockets before the event had started as well.

"Just a few more minutes, darling."

With a sigh of annoyance, Frodo forced himself to stay still for the next speech. He hated formal events like this and usually avoided them by whining to Thorin or Bilbo about how unfair it was for a pre-tween to have to endure such dreadful boringness for several hours on end. Thorin typically caved as soon as Frodo whipped out the puppy-dog eyes, as Balin liked to call them.

"It would seem that Master Gamulûn and his foremen share Uncle's passion of long-windedness," snickered Kíli a few moments later. "My ears have started bleeding."

Bilbo leaned over and discreetly swatted his middle nephew on the behind. "Hush up, zundushith."

"Did you see that? I call abuse from the hobbit."

With a quiet sigh of exasperation, Bilbo turned to stare at Thorin with a raised eyebrow. The Dwarf-King continued to stare ahead and ignore any mumblings or questionable going-ons that his nephews might be involved in. This, of course, earned Thorin a vicious poke in the side from his little husband, which was also ignored by the sable-haired dwarf. Such interactions were a common occurrence between Erebor's King and Consort nowadays, and Balin always liked to point out that they were signs of a healthy long-term marriage as well. Aunt Dís just said that they were a pair of thick-headed dolts.

"Uncle Bilbo..."

"Only a little longer now, sweetheart," soothed the older hobbit. "We don't have to stay for the actual opening, but please respect the speeches. Even if they are abominably boring and dwarvish."

Erebor's King just stared at his husband.

"What? You can't deny that you and your kinsmen like to hear yourselves talk," said Bilbo. "Do I need to remind you of the Stonefoot speech two summers ago?"

Thorin looked visibly pained at the reminder. All three of their nephews snickered at this, their bums and feet aching at the mere thought of the Stonefoot ambassador's two hour long speech. He had rattled on and on and on until Bilbo had finally lured him off stage with promises of a grand feast that couldn't be postponed any longer without the possibility of spoiling. Frodo looked at his smaller uncle after those thoughts had passed, silently urging him to bribe the speech-rambler with good like he'd done so many times in the past. With a sigh of resignation, Bilbo stepped forward to handle the situation himself.

And then the tremors started...

"Thorin?" hissed Bilbo a few seconds later. "Did you hear that—"

Less than five seconds later, a giant crack opened up between Frodo's feet, his hands scrambling for purchase as the ground dropped out from under him. The little hobbit felt his shirt being pulled in multiple directions, screams echoing throughout the chamber as another explosion went off above them.

"Uncle!"

In Frodo's opinion, there were a lot of funny things about explosions. They kinda took you by surprise and never seemed to follow a schedule. Both of those things were very distressing to hobbits, who liked neither surprises nor disrupted schedules. And it didn't matter what crafty master plan Nori could come up with...the ground bucking under your feet and a couple tons of mountain water landing on your head was gonna put a bit of a dent in it.

"Get away from the center! Off to the sides, you fools! Move it!"

Of course, being the perfectionist that he was, Nori took it personally. Frodo almost expected Erebor's spymaster to have this huge flow chart drawn up. With all those little arrows that Uncle Thorin liked to use, right? One that sent everyone down to a little rectangle on the bottom corner of the chart that said _Plan J,_ just in case of yet another assassination attempt by the Ironfists.

Frodo wasn't quite sure what _Plan J_ would be, but he had a good feeling that he and everyone else in Erebor would be following it. However, at that very moment, all Frodo was trying to do was not drown, because something very big and very nasty has just gone off directly underneath their feet and now he was falling along with a ton of water into Erebor's lower reaches.

And he wasn't the only one. Frodo could hear Dwalin coughing and choking and trying to swear, but he was also getting farther way. That frightened Frodo, because Dwalin was the toughest and strongest dwarf he'd ever met, and being near Dwalin always meant safety. Nobody messed with Dwalin and came out of it with all of their limbs, so the same had to apply to crazy explosions and raging rivers, right?

"Dwalin! Uncle Dwalin!"

Somewhere nearby, Frodo could hear Nori issuing orders for Fíli to snag Bilbo like he knew this was going to happen all along. Unfortunately, he clearly didn't expect this and Frodo could hear it in his voice, that little snap of tension that said: _Mahâl's whiskers, we're not gonna be undone by some stupid, arrogant Ironfists again_. Because he's Nori, and nothing gets the better of him.

The last thing Frodo heard before he was churned under by a bunch of river water and sediment was a loud splash. It scared the young hobbit, because diving into Erebor's newest natural waterslide wasn't smart by anyone's definition. After that, he didn't have time to think about it. The surface had just disappeared and Frodo was stuck in deep water that he couldn't see through, banging against hard rocks as he was then sucked right down through narrow, ancient pipes that had once been used to funnel bathwater up to Erebor's communal springs. The water was moving so fast that it was nigh-impossible to come up for air, and there was so much muck and churned up water that it was almost like having a shower nozzle jammed into your face. And Frodo was still falling a long way, which was really weird and didn't match up with the old blueprints he'd nicked from the archives last winter.

Of course, as Frodo had learned from those blueprints, there were a whole bunch of layers to find under gigantic dwarven cities like Erebor and Khazad-dûm—aqueducts and old catacombs and abandoned seams and such, and let's not forget the huge spooky underground area with all the creepy monsters that Bofur liked to tell stories about—but how powerful was that explosion to destroy such a large portion of the mine entrance?

Frodo really hoped that no miners had been down in the nearby tunnels when the explosives had gone off. Erebor's oldest seams went a _very_ long way down and the water that was pouring down from the upper branches of the River Running could easily trap the unsuspecting dwarves in the mines. And then the floor seemed to drop out from underneath Frodo yet again and he was pulled back to the hazardous descent that he was making into Erebor's depths.

The faunt screamed, stomach jumping up into his throat. Everything was pitch black.

Now Frodo was seriously beginning to panic. It didn't help that whenever he managed to break the surface and take a gasp of air, he was then pulled right back under into the darkness of the water. There was no light this far down in Erebor and Frodo barely had time to process that before he was banging into rock and being thrown straight into free fall. He had no idea how far down it was and he was effectively blind, not knowing when or what he was going to hit at the—

As it turned out, it was metal. The faunt landed heavily along what felt like rusted pipes, uneven and creaking underneath his slight weight because everything was unstable this far down in Erebor. The fall knocked the breath right out of Frodo, his lungs and limbs aching from fighting against the current. Two of his fingers were bent at strange angles and Frodo could feel something sticky on his elbows and forehead. The water was still pounding down on the little hobbit, and it was clear that he wouldn't be able to stay there for very long. Frodo's hands scrambled for purchase and he felt the pipe creak ominously beneath him.

Despite not being able to see anything, Frodo could still hear just fine, and the water was falling a long, _long_ way. Actually, it didn't sound like the water was hitting anything as it continued to plummet past him. That alone freaked Frodo out beyond comprehension.

Feeling around the pipe with cautious fingers, Frodo tried to figure out which direction would be the best to shimmy along, maybe towards a wall or opening or anywhere that was a little more stable. And then he could try to find a tunnel of some type; Frodo knew for a fact that Erebor was riddled with them. The sheer terror and scope of having to get back to his uncles and the upper city while stuck in complete darkness hadn't really set in yet.

"Oh, Mahâl's hammer..."

Fighting to get his breath back, Frodo attempted to balance as best he could on the back of this huge, creaky pipe. The water was pouring down around him and a loud series of booms could still be heard from far above. Frodo knew that the logical thing to do was to get out of the water's path and figure out where to go from there, but he was still too scared to move an inch at that point. The pipe was sloping just slightly downward, so following it should be okay. Or perhaps up? Which was better?

"I'm too young for this."

The faunt hesitated, and then something cracked and groaned and shifted down, and suddenly Frodo wasn't so much balanced on the pipe as he was swinging downwards with an entire section of the ancient pipe as one of the joints finally gave way.

"No, no, I don't wanna die!" sobbed Frodo. "Oh, Eru! Ahhhhh!"

And then it suddenly stopped, still semi-attached to the other end of the pipe. Now Frodo was clinging for dear life, sliding down the pipe bit by bit despite his desperate grip, all the while listening to the long, ghostly echo of water hitting ground solidly somewhere below. Frodo screamed when the pipe lurched yet again. It was a girlish screech of a scream, but Frodo really didn't care at this point.

"Mahâl! This can't be happening. Oh Eru, I'm so sorry for stealing Uncle Dori's cookies. I'll never do it again. I promise, I'll never, ever—"

A sudden thump rattled the whole pipe and Frodo slid a few more feet down, nearly falling off the edge before a large hand shot out of the darkness and latched around his wrist. It wasn't gentle by any means and those huge fingers were practically grinding his delicate bones together. Frodo screamed again in surprise, both due to the grabby hand and because the pipe section he'd been clinging to finally gave way entirely. There was a loud groaning of metal on metal and then a jarring squealing as the old joints cracked, Frodo's hair standing on end from the monstrous sound. And then Frodo was hanging in the darkness, water raining down around him, the unknown hand clamped like a vice around his wrist to keep him from falling.

The little hobbit screamed through the whole thing, too.

"Frodo!" And that was _Uncle Thorin's_ voice. "Stop screaming and give me your other hand! Give it to me, Frodo!"

The Dwarf-King was yelling at Frodo, desperately trying to be heard over that thundering water and falling pipe and his nephew's high-pitched screams. It didn't really sink in at first, but then Frodo realized that the person crushing his wrist was his _uncle_. The faunt felt like crying because he wasn't _alone_ now. Uncle Thorin was here and he always made things better. Of course, how his uncle had gotten down here was puzzling, but Frodo wasn't about to complain and he'd long since given up trying to figure out how the adults in his life did half the things they did.

And once Frodo came to terms with what had just happened, reality reasserted itself and he realized that his uncle's position couldn't be all that good, either. Thorin's face was very close to Frodo's, but he was hanging onto the faunt's wrist. It didn't take long for Frodo to work out the logistics behind that—his uncle was upside down. Mahâl! What was he doing, hanging onto the broken pipe with his toes?

"Uncle Thorin! How'd you—"

"Hush, mizimith," grunted the Dwarf-King. "I've got you. Can you give me your other hand?"

Frodo swung uselessly for a second before gritting his teeth and swinging his other arm up into the darkness. Thorin caught his other wrist a bit more gently this time, and for a moment they both just hung there, listening to the last descent of the broken section of pipe. Frodo flinched at the sound. He then realized that they were both effectively blind and his uncle probably hadn't known where Frodo was until he'd screamed like a little girl.

Who said panicking wasn't useful?

"Okay, I need you to listen to me, Frodo."

The King Under the Mountain was hanging upside down in the middle of the great underdark of Erebor, weighed down by a half-hysterical hobbit in the middle of a bunch of pipes and water and rock and who knows what else that were conspiring to kill them, and Thorin still managed to sound like he had a plan. Frodo was now convinced that his uncle wasn't all right up in the head. Maybe he'd been hit with a stone as a dwarfling?

"I'm going to swing you back up to the pipe."

Well, no one ever said that his plans were as good as Uncle Nori's. "But the pipe's broken!"

"Not all of it," he yelled back. The water was still dropping down in a heavy waterfall right next to them. Well, at least they weren't in its direct path now. Something warm dropped down onto Frodo's nose, just a drop or two. Ewwww, his uncle had spit on him. "We can't get out of here like this. I need you to hold your own weight for just a few seconds. Can you do that for me?"

In other words, Thorin needed to be the right way up before he lost his grip. How he was still holding on was beyond Frodo's comprehension. Frodo yelled an affirmative and then he was swinging in the darkness at a speed that was downright unsettling. His stomach lurched and with horror, Frodo realized that the only way his uncle could get that kind of speed straight away was if he'd kicked off of something. So, how on Arda were they not falling? And then Thorin swung them back the other way with a loud grunt of exertion and a filthy Khuzdul curse and his grip became so bone-crushing for a second that Frodo yelped in pain. The faunt felt completely disoriented in the pitch black as his uncle wrenched him up, half twisting himself...

…and then Thorin let go.

It didn't take long for Frodo to figure out what his uncle had planned. Stomach stuck in his throat, Frodo instantly spread his arms and legs and tried to focus on where that damn pipe was in the darkness. He could hear the constant fall of water off to his right and Frodo knew that that was where the broken pipe length was. His uncle's aim was true. That didn't stop Frodo from screaming his lungs out, though.

And there he went, landing with a hobbit-y clumsiness on the pipe. Then it gave out right under his hairy little feet.

Frodo jumped again with a yelp, trying for a piece of pipe or wall or anything that wasn't falling. He had barely landed on a solid surface before realizing, as the shuddering got worse under him, that the whole thing was going to come down any second now. And where was Uncle Thorin? Frodo was completely and utterly terrified. All he wanted was his uncles and his aunt and his cousins and a warm cup of Dori's tea and his uncle couldn't have fallen with the pipe, he couldn't have left Frodo here to—

"Uncle Thoooooorin!"

Apparently, this screaming thing made Frodo a really easy target for dwarves with night-vision eyeballs. Thorin collided with him not even two seconds later, left arm snaking around Frodo's back and holding tight. Yet again, this didn't stop him from screaming like a Dyrian banshee. Aunt Lobelia would've been _so_ proud.

"It's okay, Frodo. I've got you."

The Dwarf-King placed a quick kiss on Frodo's brow, his heart pounding loud enough for the young faunt to hear through his tunic and over the rushing water around them. Balin always said that a person's grip could tell a lot about them. So, in that moment, Frodo assumed that his uncle's ridiculously tight grip meant that he wouldn't be letting go of his youngest nephew any time soon. And Frodo was perfectly happy with that decision, too.

"Can we please get down?" begged Frodo around tears. "I just wanna get down, Uncle Thorin. Please get us down."

He said nothing. Of course, he said nothing. His dwarven uncle had never been the talkative type. But Frodo really didn't care about that right now. Thorin was much warmer than the pipe was, and they were definitely not falling to their doom anymore. They were swinging again, actually. His uncle had been carrying a grappling hook earlier; all of the miners used them to scale the sheer walls of Erebor's deepest mines. Frodo maneuvered himself so that he could firmly latch his arms around Thorin's neck, freeing up his uncle's left arm because they were really gonna need it if Thorin was planning to do what Frodo suspected he was going to do.

"Hang on tight," Thorin finally said.

Frodo knew that Thorin wouldn't let them fall. His uncle was too smart and strong to ever let something like that happen. And Frodo's fingers were now starting to really hurt, but his uncle had bigger things to worry about. All Frodo could do was hold on and wait for his uncle to get them down somehow, which seemed to involve using the grappling hook and finding places along the wall. At one point, Frodo heard the scrape of something and he was pretty sure it was rope or maybe a chain of some sort. His uncle braced against an unsteady or useless outcropping every couple moments and tried to work out where to go next. Frodo still couldn't see a thing, but Uncle Thorin and most dwarves were far more accustomed to working without sight than a hobbit fauntling.

He really hoped that that counted for something in this crazy mess.

"Uncle..."

"It's alright, mizimith. I've got you. Just hold on tight, okay?"

Frodo buried his face in Thorin's thick hair. "It's so dark down here. Can you see?"

"Well enough."

Another kiss landed on Frodo's tear-stained cheek. "Am I too heavy?"

"Never."

Of course, when they finally did go into freefall, Frodo screamed again and wondered if maybe the rope had given out. But Thorin didn't say anything and his other arm had wrapped around Frodo, so the faunt figured that the fall was deliberate. And then they landed in mud and water and went sliding onto their butts, but that was definitely solid ground beneath all the dampness. It was terribly slippery, but it was also safe. More or less. Frodo could still hear water pouring down, getting slower now. It was going past them.

So, Uncle Thorin had found a ledge or something. Frodo hoped it would hold them.

* * *

This whole story-arc was inspired by the Stone Giants/Goblin/Gollum Cave scenes, a portion of the old _Dungeons and Dragons_ games (hence, the title name), and a National Geographic show that I watched last year about the world's oldest and most intricate sewer and aqueduct systems. And since I'm no expert on this subject, you can thank a civil/urban engineering friend of mine for the technical subjects. He really knows his stuff. I hope everyone the first chapter so far and, as always, suggestions are welcome.


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